This is a proposal for a Philips 420 Transmission Electron Microscope with accessories for energy dispersive X-ray spectroscopy. The instrument will be used primarily by five investigators with various research projects in biological sciences, including: retinal cell biology, genetics and development of Tetrahymena, cytoskeleton, and the study of synaptic vesicles. All investigators have current NIH peer-reviewed research grants. It is estimated that their use can potentially account for 100% of a normal 40-hour week. However, since actual use will certainly vary, the microscope will be made available to other users, with priority given to those with current NIH support. The instrument will be maintained by the Institute of Environmental Stress. Technical support of the microscope and help with specimen preparation will be provided by career staff.